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JDM RPM speed to gear mod

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Old Dec 27, 2010, 09:07 AM
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JDM RPM speed to gear mod

I noticed my WGDC/per gear wasn't behaving as I'd expected on my JDM Evo VII. A bit of messing around and I have come up with the tables attached which log correctly on my car using 96530709, should work for other JDM cars with 5 speed boxes as well.
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Old Dec 27, 2010, 12:25 PM
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The "RPM/speed to gear" values matter what tranny you have and the size of your tires.

Use MRFREDs "Evo gear ratio calc" excel sheet to correctly setup that table.
Old Dec 27, 2010, 12:33 PM
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Thanks, I'm aware that the tyre sizes and transmission affect the calculated gear. The difference here is that the JDM cars use KPM and the tephra ROMs are set up for MPH. Note, most JDM cars have a converter for countries that use MPH, but this usually affects the speedo and ECU, hence things being off.

Mrfreds sheet is again for MPH. I used empirical data to confirm this data after doing a bit of calculation.

link to mrfred's excel

Good to mention this is a stock GSR 5 speed box with 234/45 17" tyre ( Toyo R1S actually), the above values should be a good starting point for most cars similar to mine.

Last edited by burgers22; Dec 27, 2010 at 12:43 PM.
Old Dec 27, 2010, 12:43 PM
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Originally Posted by burgers22
Good to mention this is a stock GSR 5 speed box with 234/45 17" tyre ( Toyo R1S actually), the above values should be a good starting point for most cars similar to mine.
Yep, your setting should work for anyone with the same tranny and sized tires.
Old Dec 27, 2010, 02:41 PM
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Originally Posted by burgers22
Thanks, I'm aware that the tyre sizes and transmission affect the calculated gear. The difference here is that the JDM cars use KPM and the tephra ROMs are set up for MPH. Note, most JDM cars have a converter for countries that use MPH, but this usually affects the speedo and ECU, hence things being off.
depends on where the speedo converter is fitted ,if its fitted on eng bay side of loom it affects ecu and speedo, if converter is fitted behind the dash cluster it affects speedo only.
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